Abstract
Low-prevalence search targets are missed disproportionately more often than high-prevalence targets (Wolfe et al., 2005). Such errors have been attributed to multiple sources, including shifting decision criterion (Wolfe, et al., 2010), target recognition errors (Godwin, et al., 2014; Schwark et al., 2013), and motor response errors (Fleck & Mitroff, 2007; Rich et al., 2008). However, recent findings indicate that the mental representation of the target has a substantial impact on later search performance (Schmidt, et al., 2014). Furthermore, when a difficult search is expected, a more detailed target representation is maintained in visual working memory (VWM; Schmidt & Zelinsky, 2017). In the current study, we examined whether the increased difficulty associated with a low-prevalence search affects the VWM representation of a target, as measured by contralateral delay activity (CDA). Participants were cued with a pictorial preview of two different target stimuli (200 ms), drawn from 18 potential real-world object target categories. CDA was assessed in the delay period after preview offset (1000 ms) but prior to search. Targets and distractors consisted of 22 real-world objects evenly drawn from the previewed categories. Target prevalence was blocked with order counter-balanced across observers. High-prevalence search consisted of 90% target present trials and low-prevalence search consisted of 10% target present trials. Consistent with previous reports, preliminary results suggest that target detection accuracy decreased in low-prevalence (42%) relative to high-prevalence search (79%). Interestingly, preliminary results also indicate that low-prevalence target-related CDA (M = -0.79) may be larger than high-prevalence target-related CDA (M = -0.39). These early findings suggest that the expectation of a difficult low-prevalence search results in more target details extracted from the preview. This raises the intriguing possibility that some low-prevalence misses could be avoided by optimizing the target representation.